Conventional overhead cranes include a bottom block that, in combination with an upper block and a drum, raise and lower hooks or other lifting mechanisms attached to the bottom block. Such overhead cranes are often used in reactor facilities to transform or transport fuel bundles between a reactor building and a containment building. In some facilities, the components of the crane must pass through a 7 foot high by a 4 foot wide door into a containment room that is surrounded by 4 feet of concrete so that the crane can be installed therein. The crane is typically designed to be installed on two existing under hung I-beams that are about 16 feet off the floor of the containment room.
The overhead crane is used to engage trunnions of a cask and to lift and move the cask to a spent fuel pool. The crane then lowers the cask into the spent fuel pool, where the cask is filled with spent fuel rods. The crane is then used to raise the cask from the pool. The top of the cask should be clear of any obstructions to allow loading of the spent fuel rods into the cask. Therefore, the crane must be disengaged from the cask during the fuel loading process and reengaged once the fuel loading process is complete.
Generally, given the dimensions of the reactor facility, there is little clearance room between the trunnions of the cask and walls of the spent fuel pool. Bottom block assemblies of current cranes use C-shaped hooks to engage the cask trunnions. However, such hooks do not function properly because the thickness of the hooks is greater than available space between the cask trunnions and the spent fuel pool walls in all horizontal directions. Accordingly, there is a need in the art for an improved a bottom block assembly for use with an overhead crane.